Valve plate body for axial piston device

ABSTRACT

Valve plate body for axial piston device, comprising at least two superimposed rigid discs, each having valve openings, and one layer of resilient material between each adjacent pair of superimposed rigid discs, said layer of resilient material being thinner than each of said rigid discs and at least surrounding said valve openings.

States P310 11 1 Widmaier 1 Sept. 4, 1973 [54] VALVE PLATE BODY FOR AXIAL PISTON [56] References Cited DEVICE UNITED STATES PATENTS [75] Inventor: Dieter wldmaiel, 1 611113611, 3,056,426 10/ 1962 Hauser l37/625.2l X Germany 3,131,605 5/1964 LaBol'dem 137/625.l5 2,807,280 9/1957 Kittredge 251/304 X 1 um R0118" Bosch Gmbfl, Stuttgart, 3,302,528 2/1967 Rosenhafi.... 91/130 Germany 2,218,034 10/1940 Bartosch 308/160 X [22] Filed: Dec. 24, 1970 Primary ExaminerHenry T. Klinksiek 1 pp 101,367 Attorney-Michael s. Striker [30] Foreign Application Priority Data [57] ABSTRACT July 11, 1970 Germany P 20 34 501.1 Valve plate body for axial piston device comprising at least two superimposed rigid discs, each having valve [52] US. Cl 137/625.21, 277/233, 91/180, openings, and one layer of resilient material between 308/160'251/304 each adjacent pair of superimposed rigid discs, said [51] Int. Cl. Flfik 11/02 layer of resilient material being thinner than each of [58] Field of Search 251/304; 308/160;

I a I 4 ss-m said rigid discs and at least surrounding said valve openings.

13 Claims, 7 Drawing Figures PATENTEDSEP 4191:

SHEET 1 OF 2 Fig.7 l 7 INVENTOR DieterWIDMAIER 2/( his ATTORNEY PATENTEnssr 4191s 3.756279 SnEEI 2 m 2 Fig. 2

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I I a 2 INVEN'TOR Dieter WIDMAIER his ATTORNEY 1 VALVE PLATE BODY FOR AXIAL PISTON DEVICE BACKGROUND OF THE INVENTION Valve plate bodies are well known, their use in axial piston machines being for instance described in US. Pat. No. 3,1 31,605, entitled Flat Valve for Hydraulic Machine.

Valve plate bodies in contrast with valve plate surfaces, where such valve plate surfaces are an integral component of the housing of the machine, have the advantage that after a certain amount of wear or after any damage, they can easily be exchanged. This is simpler and less time consuming than repair of valve plate surfaces where the valve plate is part of the machine housing. It is also less expensive and less time consuming than replacement of that section of the valve housing which contains the integral valve plate surface.

In operation, valve plates are subjected to varying forces, temperature fluctuations and above all, temperature differences in different portions thereof; these factors give rise to forces which in turn lead to deformations of the system. The deformations or dislocations result in gaps between the cylinder valve and the valve plate on the one hand, and between these components and the supporting housing of the machine on the other hand. As a consequence, there is considerable leakage and the efficiency of the machine suffers thereby.

SUMMARY OF THE INVENTION It is anobject of the invention to devise a valve plate which minimizes leakage at its contact surfaces and thereby maintains the efficiency of the entire'machine at a high level.

In accordance with the invention, this objective is achieved by providing a valve plate body comprised of at least two rigid discs and, between each pair of adjoining rigid discs, a firmly attached layer of flexible material which surrounds at least the valve openings of the valve plates and is thinner than the discs of rigid material.

As a result of these measures, the valve plate body is elastically deformable in theaxial direction, and as a result the above-mentioned deformations are diverted at least in part into portions of the valve plate body which are not located at the contact surfaces. In this way the formation of gaps is effectively avoided, and leakage is very substantially reduced.

A further advantage of thevalve plate body in accordance with the present invention results from the fact that elasticity is needed over the entire region rather than merely in certain zones. By proper shaping of the assembly, it is possible to increase the elasticity in specific regions particularly in regions near the periphery of the valve plate body where the deformations in general are greater than in the inner zones.

The flexibility of the system can be increased by making it of several alternating rigid and elastic layers.

Constructions in accordance with the present invention are particularly suitable for machines which must operate at very high hydraulic pressures. In this case, the elastic layers must be relatively thin in order not to be pressed outwardly by the pressure from the control slots.

Further constructions in accordance with the invention are given in the description of the preferred embodiments, drawings, and the claims.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a cross section through a valve plate body;

FIG. 1a is a plan view of a valve plate body;

FIGS. 2, 3 and 4 are sectional views through variations of constructions in accord with the present invention;

FIG. 5 is a perspective view of another form of the invention; and

FIG. 6 is a sectional view through a modification similar to that shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The valve plate body of the construction variation shown in FIG. 1 consists of an upper rigid disc 1 and a lower rigid disc 2 which are superimposed on each other. Between the two opposing faces of the discs is a layer 3 of a resilient material, such as rubber, polytetrafiuoroethylene or another suitable elastomer. This elastic layer is firmly attached to the adjacent faces of the rigid layers by means such as cementing, and in the case of rubber by vulcanization. The layer 3 which, for example, may be in the form of a disc, is thinner than the layers of rigid material; this will be discussed in more detail below.

Theassembly prepared in this way constitutes a valve plate body which can be taken apart only with difficulty; the construction offers substantial resistance to turning of one rigid plate with respect to another. For further assurance against such relative rotation, a pin 4 is provided which passes through the upper disc I by means ofa clearance hole and which seats in a blind hole in the lower disc 2..The usual through-going con-- trol slots 5 and 6 are'provided in the valve plate body.

In accordance with the usual practice, the valve plate body is mounted in a housing 7 of the axial piston machine which is indicated by the dash and dot lines. 0n the lower side of the valve plate body, that is, the lower end face of the disc 2, which is turned away from the flexible disc 3, rotates the cylinder barrel 8 of the axial piston device. It is desirablethat the rigid disc 2 be made of a material with good anti-friction properties, such as bronze or brass.

In operation of the axial piston machine strains are produced in the valve plate body as for example as a result of unequal temperature rise in various parts of the valve plate body. For example, the temperature of the oil used as the hydraulic medium is higher at the output side of the valve plate body than at the intake side. The frictional forces originatingin the rotation of the cylinder barrels against the valve plate body cause a greater temperature rise at the periphery than at the internal portionssince the rate of rotation is greater at the outer portions. Finally, the various forces operating on the valve plate body are unequally distributed and oriented. All of these forces give rise to deformations of the valve plate body as a result of which small gaps between the contact surfaces arise which lead to undesired leakage of oil. The efficiency of the device is thereby lowered.

Valve plate bodies made in accordance with the present invention avoid these difficulties for the most part in the region of the resilient layer 3; in this region the resilient layer 3 accommodates the forces substantially completely. The contact surfaces remain more even than has been the case with previous valve plate bodies, in addition to which formation of gaps is minimized and the leakage of oil is strongly decreased.

In axial piston devices which operate at very high pressures, the elastic material must be as thin as possible in the region of the valve slots; a desirable thickness is about 1 mm. Otherwise, under certain circumstances, there arises the danger that the layer 3 will be pressed out by the pressure forces of the hydraulic medium. Since the gaps which result from the deformations are very thin, somewhat in the neighborhood of tenths of a millimeter, the layer 3 can be completely retained.

In order to increase the flexibility of the valve plate body, the variations shown in FIG. 2 and 3 can be employed. The valve plate bodies shown in FIG. 2, consist of an upper rigid disc and a lower rigid disc 11. Starting at the outer periphery and extending inward to a point exterior to the slot 5. each of the discs 10 and 11 has a recessed portion, respectively, 12 and 13. The rigid discs 10 and 11 are so oriented that the recessed portions face each other thus forming a circumferential groove. The resilient layer 14 is so shaped that it fills the circumferential grooves between the two rigid discs. As a result, the outer zone of the system is more elastic than inner zones.

A similar arrangement is shown in the embodiment of FIG. 3. The lower rigid disc 3 is constructed exactly as in the example of FIG. 1, while the upper layer 15 external to the valve slot 5' has a bevel 16, which is so arranged that the thickness of the disc 15 decreases outwardly. Theresilient layer 17 again fills the entire groove.

The valve plate body according to the example of FIG. 4 consists of a stack of a larger number of rigid discs 18-21. Between each pair of discs is disposed a layer 22 of the type shown in the embodiment of FIG. 1.

As shown in the example of FIG. 5, it is not necessary for the resilient layer to fill the entire space between two adjacent rigid discs. It suffices if the region around the valve slots is completely surrounded by the resilient layer 23, 23'. These resilient layers reach from the outer periphery to the inner periphery of each rigid disc and surround the valve slots 5 and 6 completely. Such an arrangement is suitable, for instance, where the machines operate in medium or low pressure ranges. It can thus be stated that the resilient layer may be a disc or a segment of a disc.

As is shown in the embodiment according to FIG. 6, where the hydraulic pressures in the neighborhood of the high pressure side of the valve plate body are very high, then extrusion of the resilient material from the region around the high pressure slot can be avoided by making the resilient material in the form shown at 24. The protective body 24 is joined firmly to the discs 1 and 2, and constitutes a lining around the periphery of the slot.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims,

I claim:

1. A stationary valve plate body for an axial piston device, said valve plate body comprising two superimposed rigid disks, each having valve openings; and a layer of resilient material between said superimposed rigid disks and at least surrounding said valve openings, at least one of said rigid disks being thinner in the region of said disk between its outer periphery and the adjacent valve opening so that the space between said disk is wider in said thinner region of said one disk than in the remaining regions of said one disk, said space between said disks about said valve openings being filled by said layer of resilient material and the portion of said layer between said remaining regions of said one disk and the other disk being thinner than each of said disks in the region of the thinner region thereof.

2. A stationary valve plate body as defined in claim 1, wherein said wider space tapers towards said adjacent valve opening.

3. A stationary valve plate body for an axial piston device, said valve plate body comprising a stack of superimposed rigid disks, each having valve openings aligned with the valve openings in the other of said stack of disks; and a layer of resilient material between each adjacent pair of superimposed rigid disks, said layer of resilient material being thinner than each of said rigid disks and at least surrounding said openings.

4. Valve plate body as defined in claim 3, wherein each layer of resilient material is firmly attached to said adjacent rigid discs.

5. Valve plate body as defined in claim 3, wherein each layer of resilient material is of uniform thickness.

6. Valve plate body as defined in claim 3, wherein said layers of resilient material correspond in size and configuration to the end faces of respectively adjacent one of said rigid discs.

7. Valve plate body as defined in claim 3, wherein the layers of resilient material are each of uniform thickness.

8. Valve plate body as defined in claim 3, wherein at least one of said discs is composed at least in part of material havinganti-friction properties.

9. Valve plate body as defined in claim 8 wherein said material having good anti-friction properties is selected from the group consisting of bronze and brass.

10. Valve plate body as defined in claim 3, wherein said valve openings comprise two diametrically opposite arcuate slots having the same center and equal radii of curvature.

11. A valve plate body as defined in claim 3, and including holding means for preventing said disks from turning with respect to each other.

12. Valve plate body as defined in claim 11, wherein said holding means comprises a pin passing through all of said discs.

LII

rior of at least one opening integral with said layer of resilient material and firmly joined to said disks for preventing the extrusion of said layer from the region around said opening when said valve plate body is operated at high pressure.

* t IF 

1. A stationary valve plate body for an axial piston device, said valve plate body comprising two superimposed rigid disks, each having valve openings; and a layer of resilient material between said superimposed rigid disks and at least surrounding said valve openings, at least one of said rigid disks being thinner in the region of said disk between its outer periphery and the adjacent valve opening so that the space between said disk is wider in said thinner region of said one disk than in the remaIning regions of said one disk, said space between said disks about said valve openings being filled by said layer of resilient material and the portion of said layer between said remaining regions of said one disk and the other disk being thinner than each of said disks in the region of the thinner region thereof.
 2. A stationary valve plate body as defined in claim 1, wherein said wider space tapers towards said adjacent valve opening.
 3. A stationary valve plate body for an axial piston device, said valve plate body comprising a stack of superimposed rigid disks, each having valve openings aligned with the valve openings in the other of said stack of disks; and a layer of resilient material between each adjacent pair of superimposed rigid disks, said layer of resilient material being thinner than each of said rigid disks and at least surrounding said openings.
 4. Valve plate body as defined in claim 3, wherein each layer of resilient material is firmly attached to said adjacent rigid discs.
 5. Valve plate body as defined in claim 3, wherein each layer of resilient material is of uniform thickness.
 6. Valve plate body as defined in claim 3, wherein said layers of resilient material correspond in size and configuration to the end faces of respectively adjacent one of said rigid discs.
 7. Valve plate body as defined in claim 3, wherein the layers of resilient material are each of uniform thickness.
 8. Valve plate body as defined in claim 3, wherein at least one of said discs is composed at least in part of material having anti-friction properties.
 9. Valve plate body as defined in claim 8 wherein said material having good anti-friction properties is selected from the group consisting of bronze and brass.
 10. Valve plate body as defined in claim 3, wherein said valve openings comprise two diametrically opposite arcuate slots having the same center and equal radii of curvature.
 11. A valve plate body as defined in claim 3, and including holding means for preventing said disks from turning with respect to each other.
 12. Valve plate body as defined in claim 11, wherein said holding means comprises a pin passing through all of said discs.
 13. A stationary valve plate body for an axial piston device, said valve plate body comprising at least two superimposed disks, each having valve openings; a layer of resilient material between each adjacent pair of superimposed disks, said layer of resilient material being thinner than each of said rigid disks and at least surrounding said openings; and a lining around the interior of at least one opening integral with said layer of resilient material and firmly joined to said disks for preventing the extrusion of said layer from the region around said opening when said valve plate body is operated at high pressure. 